Positrons are the anti-matter counterpart to electrons and are used in a wide variety of fields, from particle physics to medicine. Positrons may also be used for power applications, including rockets, because of the high power density associated with positrons. While several methods for producing positrons are known and are being used, the apparatus required to produce and store positrons are cumbersome and expensive. For example, one method for producing positrons involves the use of particle accelerators, which are expensive and difficult to operate. Once the positrons are produced, they must be somehow conveyed to a suitable storage apparatus, such as a Penning-Malmberg trap, for storage and later release. Of course, the anti-matter nature of positrons makes it difficult to convey and store the positrons as they quickly annihilate with conventional matter (i.e., electrons). As a result, only a very small fraction (e.g., 1 in 105) of the positrons actually produced can be conveyed to the storage system.
Another method for producing positrons involves the use of certain radioactive isotopes, such as sodium-22, which produces positrons as a result of radioactive decay. The positrons are then moderated, usually in a tungsten “blind,” and stored in a Penning-Malmberg trap. While the use of such radioactive isotopes as positron sources does away with the need for particle accelerators, they are not without their problems. For example, first are the problems associated with the utilization of the open radioactive source (e.g., Na-22). Second, a large fraction of the positrons are annihilated within the source or the source holder before they can be moderated and stored. Third are the difficulties in transferring the positrons away from the source to the trap.
Consequently, a need remains for a method and apparatus for producing and storing positrons that does not suffer from the disadvantages of current methods.